The way I would separate the shell fragments from the sand would be by using a filter. As shell fragments are larger than sand. So I would use a filter with 2 mm spaces to separate them. Now, for the sand separation from the water, I would heat the water so it would evaporate and connect a tube to another recipient making the sand stay in the first tube and the water vapor cools in the tube to precipitate in the other recipient. Three mixtures I have prepared at home are chocolate milk, coffee and cream, and lemon juice and tea.
Explanation:
To understand this answer we have to remember a few things. First, mixtures always have solute and solvent. The solvent is the most liquid component of the mixture and it can incorporate the more solid element in its composition to carry it. Now, there are several methods to separate them, barrier methods like filters are the first and more basic ones, as they are aimed to separated big solutes. While evaporation can be used to separate two very liquid elements. Like distillation of alcohol to separate the most concentrated oil from the alcohol.
